In a wireless access standard being applied to a physical layer of an IEEE 802.16d wireless metropolitan area network (NAN)-OFDMA, a downlink access standard from a base station to a subscriber station and an uplink access standard from the subscriber to the base station in a time-divided manner are provided.
When the subscriber transmits downlink channel quality information (CQI) to the base station through an uplink by measuring a downlink channel quality, the subscriber station transmits the CQI through a predetermined subchannel of the physical channel. At this time, the predetermined subchannel is determined by a cell identifying number (cell ID) of the base station, and allocated to respective subscribers according to the number of CQI channels of the base station. In addition, a downlink channel quality value measured by the subscriber station is quadrature-modulated to the CQI, and transmitted to the base station.
A channel for automatic repeat request (ARQ) acknowledgement/negative-acknowledgement (ACK/NACK) is also transmitted in a like manner of the CQI, but a subchannel allocation method is different.
Therefore, demodulators corresponding to the number of transmit channels are required since the base station demodulator detects and demodulates the CQI and the ARQ ACK/NACK channel transmitted from a plurality of subscriber stations.
As prior art, “an apparatus and a method for coding and decoding of CQI in communication system using high speed downlink packet access scheme” has been disclosed in Korean Patent Application No. 2002-16561 filed in the Korean Intellectual Property Office on Mar. 26, 2002, which relates to an apparatus and method for coding and decoding CQI in a code division multiple access (CDMA) communication system using a high speed downlink packet access (HSDPA), and more particularly to an apparatus and method for coding and decoding CQI to insert a pilot signal into a high speed-physical downlink shared channel (HS-PDSCH) and to transmit the HS-PDSCH having the pilot signal inserted therein such that power of a high speed uplink control channel can be controlled.
In this patent, the CQI is transmitted by coding and decoding the CQI in the CDMA communication system.
In addition, “an apparatus and method for transmitting and receiving forward channel quality information in a mobile communication system” has been disclosed in Korean Patent Application No. 2002-51632 filed in the Korean Intellectual Property Office on Oct. 29, 2002, which relates to a mobile communication system that supports a multimedia service including voice and data services, and more particularly to an apparatus and method for transmitting and receiving information indicating a forward data rate between a mobile station and a base station.
In this patent, relative and absolute values of the CQI measured in the downlink are defined, and a method for transmitting the CQI in the CDMA communication system has been disclosed.
In addition, “a method and apparatus for channel quality measurements” has been described in Korean Patent Application No. 2004-7005680 filed on Apr. 16, 2004, which relates to a method and apparatus for measuring an OFDM channel quality.
In the HSDPA of a universal mobile telecommunications system (UMTS), the CQI is transmitted through a channel quality information channel (CQICH), and is modulated and coded by a CQI coder and a Walsh modulator. That is, the subcarrier of the subchannel is quadrature-modulated in the conventional HSDPA method.
In other words, the CQI and ACK/NACK in the OFDMA method may not be demodulated in the conventional HSDPA method since the HSDPA method is different from an OFDMA standard in which coding and modulating operations are not performed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.